Method of continuously casting solid state cylinders

ABSTRACT

Solid round castings suitable for direct drawing into tubes are continuously cast by pouring metal molten metal into a rotating bottomless mold at a point eccentric to the axis of the mold, and continuously withdrawing the casting from the bottom of the mold. The mold should be rotated at a number of rotations per minute equal to 6,000-18,000 divided by the diameter of the mold in millimeters. Improved results are obtained by vertically reciprocating the mold as it rotates.

[56] References Cited UNITED STATES PATENTS 2,752,648 7/1956Robert.........................

FOREIGN PATENTS 1,181,997 1/1959 France.........................

850,245 10/1960 Great Britain... 984,053 2/1965 Great Britain... 256,6451/1928 Primary Examiner-J. Spencer Overholser Assistant Examiner-R.Spencer Annear Attorney-Holcombe, Wetherill & Brisebois ABSTRACT: Solidround castings suitable for direct drawin Aulnoye-Aymerles; Louis Babel,Sauvlgny-Les-Bois, both oi, France 21 Appl. N0. 110,421

Feb. 14, 1968 [45] Patented June 8, 1971 Societe elvile dlte: SocleteClvile DEtudes De Centrifugatlon Paris, France [32] Priority Sept. 4,1964, Mar. 3, 1965 France PV 987,183 and PV 7,785 Continuation-impart ofapplication Ser. No. 483,210, Aug. 27, 1965, now abandoned.

United States Patent [72] Inventors Pierre Peytavln [22] Filed [73]Assignee 8 into tubes are continuously cast by pouring metal moltenmetal into a rotating bottomless mold at a point eccentric to the axisof the mold, and continuously withdrawing the casting from the bottom ofthe mold. The mold should be rotated at a number of rotations per minuteequal to 6,00018,000 divided by the diameter of the mold in millimeters.Improved results are obtained by vertically reciprocating the mold as itrotates.

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METHOD OF CONTINUOUSLY CASTING SOLID STEEL CYLINDERS This application isa continuation-in-part of our prior application, Ser. No. 483,210 filedAug. 27, 1965, now abandoned.

Most processes which are in current use for manufacturing steel tubesbegin by removing shavings from sections obtained by rolling ingots castin a conventional manner.

It will be readily understood that the billets obtained in this mannerare relatively expensive, and that this constitutes an increasinghandicap in selling tubes manufactured according to said processes.

Processes are also known whereby bars or billets of polygonal section,and especially square section, are made by continuous static castingfrom molten steel.

Methods are also known, even though they involve some additionaldifficulties, which permit the production of steel bars by continuousnonrotating casting. Unfortunately, the round steel bars or billetsheretofore obtained by the well-known process of continuous casting havenot had the necessary qualities to permit them to be directlytransformed into tubes, bars, beams or threads (filaments) bytraditional methods.

In fact, the round bars obtained by continuous static casting have atendency to develop two types of flaws which make them unsuitable forthe manufacture of tubes.

On the one hand, their surfaces often have fissures, which in the caseof the more serious ones, are productive of flaws in the outer surfaceof the tubes, and on the other hand, it frequently happens that roundbars obtained by continuous casting have cavities in their central partswhich lead to even more serious flaws in the tubes.

Although attempts have been made to produce round bars having superiorqualities by traditional methods of continuous casting, it has not beenpossible heretofore to use them in industry because the relatively highcost of transforming a round bar into a tube involves a problem in thateven an apparently small increase in the percentage of tubes rejected isenough to absorb and even exceed the savings realized by the manufactureof round bars by continuous casting, if these round bars are lessperfect than the bars produced according to the traditional process.

The present application relates to a new process permitting thecontinuous casting of round bars, particularly of steel, from which itis possible to form tubes, bars, beams or filaments havingcharacteristics as good as those obtained from the round bars producedby processes now in use.

The present invention has for an object a new process for continuouslycasting round metal bars, this process being essentially characterizedby the fact that the continuous casting is accomplished in a cooled moldturning at a speed within a predetermined range about a practicallyvertical axis, shaping being effected by a jet of molten metal enteringat a point eccentric with respect to the axis of the mold.

According to the invention, the jet of molten metal may strike the moldat a point located in the outer third of the radius of the casting.

In addition, it may be advantageous to impart to the jet of molten metalsupplied to the mold a component of horizontal speed perpendicular tothe radius of the mold passing through the impact point.

According to one preferred method of carrying out the invention theremay be imparted to the jet of liquid metal a horizontal component ofspeed different from the tangential speed of the mold, at the point ofimpact of the jet, so as to mold the part of the metal that is stillliquid to rotate relative to the mold.

In accordance with the invention, the casting is preferably cooled afterleaving the mold by a spray of water from fixed jets, which has theadvantage of an excellent distribution of the cooling action about theperiphery of the rough casting.

Cooling of the rough casting at its departure from the mold may also beeffected by means of jets turning, with respect to the axis of thecasting, at a speed different from that of the casting.

The mold may advantageously be made from a good heat conducting metalsuch as copper, and may be cooled by a strong circulation of water.

According to the invention, the mold may have a slightly tapered shape,the smaller end of the frustoconical mold being situated at the bottom.

The mold should be rotated at a speed high enough to produce the desiredrounding and smoothing effect on the casting surface, but low enough toavoid the creation of excessive centrifugal forces. In practice thisspeed depends in part on the diameter of the casting and it has beenfound that the minimum speed of rotation, in revolutions per minute, isequal to 6,000, divided by the diameter of the casting in millimeters,and that the maximum speed for any casting is 3 times the minimum. Thusin the case of casting having a diameter of mm. the minimum speed ofrotation is 6,000/l20=50 r.p.m. and the maximum is I50 r.p.m.

The speed of extraction from the mold is naturally a function of itsdiameter. By way of example, the applicant has obtained excellentresults with extraction speeds of 60 to 80 centimeters per minute forcastings having a diameter of mm. However, extraction speeds above thismay be utilized in carrying out the invention.

An examination of round bars produced in accordance with the process ofthe present invention reveals scarcely any flaws on the surface, andinspection of macrographic sections thereof fails to show the existenceof any significant defect or appreciable porosity in the axial portionof the casting.

These remarkably good results are due to the combination of the rotationof the mold and the feeding of molten metal through a spout sopositioned that the impact point of the molten metal is eccentric withrespect to the axis of the mold.

In fact, the elimination of one or the other of these two features leadsto results quite markedly inferior in quality as compared with thecastings produced according to the present invention.

It is believed that the improved quality of the results obtained overand above that of the round bars produced in accordance with priormethods of continuous casting, can be explained by a very greatuniformity in the formation of the solidified wall of the castingwhichthickens during cooling.

This great regularity in the formation of the wall of the casting seemsto be due, in the process according to the invention, to the fact thatthe jet of liquid metal flowing from the spout falls on a constantlychanging point on the casting, at which point its temperature decreasesrapidly, which avoids the abrasive effects of the jet of liquid metal onalready solidified parts of the shape.

In fact, it is known that one of the prevailing problems in conventionalprocesses of nonrotating continuous casting, is that of irregularitiesin the formation of the walls of the casting, which irregularitiesresult in large part from the fact that the jet of metal entering themold flows along a very unstable path which leads it to irregularly lapthe walls of the casting and to cause at certain spots a refusion of themetal which is just beginning to solidify.

It has also been shown that during the process according to the presentinvention the slag and other impurities carried along by the jet ofmolten metal collect spontaneously in the central cavity of theparaboloid of revolution formed by the free surface of the metal. Theimpurities consequently cannot cause defects on the external surface ofthe casting as is the case in those of continuous castings in which themold is not rotated. Moreover, these impurities can easily be withdrawnby reason of the fact that they are concentrated at a very accessiblepoint.

The feature of imparting to the jet of molten metal supplied to thecasting, in accordance with a preferred embodiment of the invention, ahorizontal speed component which is different from the tangential speedof the mold at the impact point, makes it possible to impart to theliquid metal contained in the casting during solidification, adifferential rotating movement with respect to the solidified portion ofthe casting which is, of

course, carried along by the speed of rotation of the mold. Thisrotational movement of the solidified part of the casting with respectto the liquid metal which it supports also contributes very efficientlyto an extremely regular formation of the walls of the casting.

The difference in speed of rotation between the solid and liquid partsof the casting is significant inasmuch as it is found that the dendritesof the casting are not radially disposed, but are disposed at a certainangle with respect to the radial direction of the casting. This angularalignment has a very favorable influence on the structure at the centerof the latter.

Another object of the present invention is to provide a new article ofmanufacture consisting of a casting produced by the continuous castingprocess just described, one of the advantageous characteristics of whichis that its dentrites are inclined with respect to the radii of itssections.

By way of example, the applicant has produced by continuous casting,round steel rods or sections directly utilizable for the manufacture oftubes by a process having the following characteristics: The round rodswere manufactured in a mold having a diameter of 140 mm. The speed ofrotation of the mold was 70 r.p.m. The jet of liquid metal struck thecasting at a point located about l mm. from the wall of the mold. Thespeed of extraction of the casting was about 70/80 centimeters perminute.

In another example of operation of the invention, a mold having adiameter of 90 mm. and a height of 220 mm. turning at a speed of 100rpm. was utilized. The casting was made of grade B steel.

The casting was extracted at a speed of l centimeters per minute, andcooled on leaving the mold by being sprinkled from stationary jets at arate of flow of 6 to 8 cubic meters of water per hour.

The impact point of the jet of molten metal was centered at about mm.from the wall of the mold.

In another example of the process according to the invention, grade Csteel was run through the same ingot mold having a 90 mm. diameter and220 mm. in height, rotating at 90 rpm. The speed of extraction was aboutI meter per minute. The casting was not cooled on leaving the mold andthe impact point of the jet of molten metal was at about 5 mm. from theedge of the mold.

The castings of circular section obtained according to the invention, byreason of their particular structure resulting from their process offormation, have marked advantages when they are utilized for certainapplications other than the conventional manufacture of tubes, in whichthey permit finished products of particularly good quality to beobtained.

A first application of these castings consists in cutting them in orderto obtain lengths directly utilizable in the manufacture of any profileswhatever by hot drawing, and especially by hot drawing processesutilizing glass as a lubricant.

Another application of the castings of circular section according to theinvention consists in utilizing them to obtain for example, throughforging or rolling, rods or filaments of reduced diameter.

The invention also includes suitable apparatus for carrying out theabove-described process, characterized by the fact that it comprises incombination: a cooled mold section rotating about a substantiallyvertical axis, means for directing a jet of liquid metal to an eccentricpoint located at the upper part of the mold, and means to extractvertically toward the bottom the castings which is thereby formed.

A further object of the present invention is to provide a process of theforegoing type in which the mold is vertically reciprocated during thecasting process.

The amplitude of the reciprocation may be of the order of from 5 to 30mm. During this reciprocation the downward speed of the mold may beequal to or greater than the speed at which the casting is extracted,for example about 1.15 times that speed.

The upward speed of the mold may differ from its downward speed, and maybe, for example from I to 3 times as great.

The amplitude and speed of reciprocation of the mold are dependent onother casting conditions and particularly on the speed at which thecasting passes through the mold.

The combination of rotation and vertical reciprocation of the moldcauses the solidified skin of the casting to be more easily and surelyformed, because the vertical movement of the casting relative to thesurface of the mold cooperates with the centrifugal force resulting fromrotation of the mold to prevent the adhesion of areas of the skin to themold in a manner which would cause tearing of the skin.

As a consequence of the combination of these two characteristics, anypoint of adhesion which may develop are immediately separated by therelative vertical displacement between the mold and casting, while theliquid which is urged toward the mold wall by centrifugal forceimmediately reforms the skin covering the very small area over which ithas been torn loose or ruptured by such adhesion.

. This leads to better quality control and permits higher castingspeeds.

The present invention also comprises a new device for carrying out theprocess which has just been described, which device is essentiallycharacterized by the fact that the rotating mold is mounted so that itmay be vertically reciprocated along the casting axis and is providedwith means for causing such reciprocation.

It will of course be understood that the particular methods of using theround rods indicated above in no way limit the scope of the invention,which relates a particular means and method of manufacture of round rodsby continuous casting and the round rods produced by said method,whatever use is later made thereof.

Likewise, it is equally true that the invention is not limited tocastings made of steel, but that it concerns all cylindrical castingwhich may be manufactured by the process involved, from steel or fromalloys whose fusion temperatures are on the order of those ofconventional or special steels.

In order that the invention may be better understood, two preferredembodiments of the apparatus comprised by the invention will now bedescribed, purely by way of illustration and example, with reference tothe accompanying drawings in which:

FIG. II is a perspective view showing schematically a first apparatusfor carrying out the process according to the invention;

FIG. 2 is a vertical cross section through the device shown in FIG. 1taken along line ll-ll of FIG. 3;

FIG. 3 is a schematic plan view corresponding to FIG. 2;

FIG. 41 is a schematic top view showing the position of the impact pointof the jet of molten metal with respect to the mold;

FIG. 5 is a schematic vertical elevation showing a second apparatus forcarrying out the invention;

FIG. 6 is a schematic vertical section taken through the axis of themold shown in FIG. 5;

FIG. 7 is a top plan view of the apparatus shown in FIG. 5; and

HG. 8 is a schematic view showing the control system for the hydrauliccylinders used in connection with the apparatus of F116. 5.

Like reference numerals denote like parts throughout the several views.

In FIG. 1 there is shown a mold l which is mounted on means not shown soas to be able to turn about its vertical axis.

This mold ll is driven by pinion 2 which meshes with ring gear 3 fixedon the mold.

As can be seen in FIG. 2, mold l is cooled by water circulating incavities 4 appropriately positioned inside the mold walls.

A small spout 5 delivers a jet of liquid metal 6 which is cooled by themold and forms a casting 7 the central part 8 of which is still liquid,as can be seen in FIG. 2.

It will be noted that by reason of the rotation of the mold, the freesurface 9 of the liquid metal 8 has the shape of a paraboloid, at thecenter of which slag l0 collects and from which it can be easilyeliminated.

The drawing also shows jets 11 which spray water into cooling contactwith that portion of the casting 7 which has left the lower part of themold.

It is noteworthy that because of the rotation of the casting accordingto the invention, it is possible to spray a very large quantity ofcooling water which may, for example, be from 2 to 3 cubic meters ofwater per ton of cast metal.

FIG. 2 also shows how the casting is extracted toward the bottom bymeans of a device consisting, for example, of two pairs of poweractuated rollers 12, resiliently urged against the casting and mountedon a toothed support 13 which is driven by a pinion 14 with the samespeed of rotation as that which is communicated to the casting by mold1.

FIG. 2 also shows how pinions 2 and 14, which are mounted on a singleshaft, can be driven by motor 15.

In order to illustrate the eccentric position of the stream 6 of liquidmetal with respect to the mold, there is shown schematically in FIG. 4the inner surface of the walls of the mold, and the supply conduit 5, aswell as the liquid metal jet or stream 6.

FIG. 4 also shows the radius R of the mold as well as distances D and dwhich are the distances of the impact point of the jet 6 on the castingfrom the center of the mold on the one hand, and from its wall in on theother hand.

As has been previously indicated, the axis of the spout 6 can beadvantageously located in the outer third of the radius of the mold,which signifies that d is not more than R/3.

Turning now to the second embodiment of the invention, FIG. 5 shows theupper part of a continuous casting machine in which the mold isvertically reciprocated.

Reference numeral 21 indicates the frame which carries the first coolingmeans and the first guide rolls to contact the workpiece. These areenclosed in the housings 22 and 23 and are not illustrated since theyare of a conventional type and the details thereof form no part of theinvention.

The support for the rotary mold, which support carries reference numeral24, swings about a pivot 25 so as to clear the top 22a of the housing22, which gives access to the line along which the casting formed by themold 26 is extracted. The axis 27 of the mold is, when in operatingposition, aligned with this line of extraction.

FIG. 6 shows how the rotating mold 26 is supported by two thrustbearings 28 and 29, (which are schematically illustrated) and driventhrough a beveled ring gear 30 by a bevel gear 31 fixed to the shaft 32driven from the motor 33 through gears 34.

For the sake of simplicity the rotary joints which make it possible tocool the mold 32 have not been illustrated, since these joints are notin themselves novel.

FIG. 7 shows the ring gear 30 as well as the pinion 31, driven by themotor 33.

FIG. 7 also shows the two hydraulic cylinders 35 positioned on oppositesides of the rotating mold, as well as the hydraulic cylinder 36positioned.

The movable pistons 35a of the hydraulic cylinders 35 act on thebrackets 37 fixed to the frame of the support 24 of the rotating mold,which brackets are reinforced by the vertical webs 38 welded thereto.

The movable piston 36a of the hydraulic cylinder 36 rests directly onthe supporting frame 24.

As has been schematically shown, the upper ends of the movable pistons35a and 36a of the hydraulic cylinders have a slightly conical shape soas to insure the exact positioning of the mold 26, when they engage incorrespondingly shaped recesses in the brackets 37, in the case of thecylinders 35 and the support 24, in the case of the cylinder 36.

The pivot 25, which has been schematically shown, has the characteristicof permitting the vertical displacement of the mold support 24 when thelatter is acted upon by the cylinders 35 and 36.

On the other hand, when the movable pistons of the cylinders 35 and 36are completely lowered, the pivot 25 carries stops which keep the lowerpart of the mold 26 a certain distance above the surface 220, so thatthe mold 26 can be swun to uncover the upper of the housing 22.

FI S. 5 and 7 also, schematically show the shoe 39 from which the jet ofmolten metal 40 is ejected to strike the casting at the eccentricallypositioned point 41.

FIG. 8 schematically shows how the hydraulic cylinders 35 and 36 arecontrolled from a single pump having three cylinders 43, the pistons 44of which are simultaneously displaced by a shaft 45 provided with threeidentical cams 46, said shaft being driven by a motor 47 throughsuitable reduction gearing 48.

Conventional means are provided to compensate for any leaks which mayoccur in any of the circuits.

It will thus be seen that rotation of the motor 47 causes the periodicraising and lowering of the mold support 24, by means of the hydrauliccylinders 35 and 36.

Of course, the mold support 24 might be reciprocated by other means,such for example as mechanically controlled cams. However, the hydraulicdevice which has just been described affords great flexibility inadjusting the speed and amplitude of reciprocation of the mold 26.

We claim:

1. A process for continuously molding a solid metal casting comprisingthe steps of rotating a bottomless cylindrical mold about its main axisat a speed between 50 and 200 r.p.m. while maintaining said mold in avertical position, cooling said rotating mold, and introducing a jet ofmolten metal into said cooled rotating mold at a point eccentric to theaxis thereof, while continuously withdrawing said casting from the lowerend of said mold.

2. Process according to claim 1 wherein the point of introduction ofsaid jet into said rotating mold is located within the outer third ofthe radius of said casting but spaced inwardly from said mold.

3. Process according to claim 1 wherein said jet of molten metal has acomponent of horizontal speed perpendicular to the radius of the moldpassing through the point of impact of said jet of molten metal on saidcasting.

4. Process according to claim 1 wherein said jet of molten metal has acomponent of horizontal speed different from the speed of rotation ofsaid casting at the point of impact of said jet with said casting.

5. Process according to claim 1 wherein said mold is rotated at a speedranging from 70 to I00 r.p.m.

6. Process according to claim 1 wherein said casting upon withdrawal issubjected to a cooling water spray after passing the point of exit.

7. Process according to claim 1 wherein said casting upon withdrawal issubjected to a cooling water spray after passing the point of exit, saidspray being directed from spray means rotating about said casting.

8. A process for continuously molding a solid metal casting comprisingthe steps of rotating a bottomless cylindrical mold about its main axisat a number of revolutions per minute equal to from 6,000 to 18,000divided by the number of millimeters in the mold diameter whilemaintaining said mold in a vertical position, cooling said rotatingmold, and introducing a jet of molten metal from which said casting isto be formed into said rotating mold at a point eccentric to the axisthereof while continuously withdrawing said casting from the lower endof said mold.

9. The method claimed in claim 8 in which said mold is verticallyreciprocated while being rotated.

10. The method claimed in claim 9 in which said mold, duringreciprocation is moved downwardly more rapidly than said casting iswithdrawn therefrom.

11. The method of manufacturing an article of manufacture whichcomprises the steps of producing a casting by the method claimed inclaim 8, and hot drawing said casting.

12. The method claimed in claim 11 in which glass is used as a lubricantduring said drawing.

1. A process for continuously molding a solid metal casting comprisingthe steps of rotating a bottomless cylindrical mold about its main axisat a speed between 50 and 200 r.p.m. while maintaining said mold in avertical position, cooling said rotating mold, and introducing a jet ofmolten metal into said cooled rotating mold at a point eccentric to theaxis thereof, while continuously withdrawing said casting from the lowerend of said mold.
 2. Process according to claim 1 wherein the point ofintroduction of said jet into said rotating mold is located within theouter third of the radius of said casting but spaced inwardly from saidmold.
 3. Process according to claim 1 wherein said jet of molten metalhas a component of horizontal speed perpendicular to the radius of themold passing through the point of impact of said jet of molten metal onsaid casting.
 4. Process according to claim 1 wherein said jet of moltenmetal has a component of horizontal speed different from the speed ofrotation of said casting at the point of impact of said jet with saidcasting.
 5. Process according to claim 1 wherein said mold is rotated ata speed ranging from 70 to 100 r.p.m.
 6. Process according to claim 1wherein said casting upon withdrawal is subjected to a cooling waterspray after passing the point of exit.
 7. Process according to claim 1wherein said casting upon withdrawal is subjected to a cooling waterspray after passing the point of exit, said spray being directed fromspray means rotating about said casting.
 8. A process for continuouslymolding a solid metal casting comprising the steps of rotating abottomless cylindrical mold about its main axis at a number ofrevolutions per minute equal to from 6,000 to 18,000 divided by thenumber of millimeters in the mold diameter while maintaining said moldin a vertical position, cooling said rotating mold, and introducing ajet of molten metal from which said casting is to be formed into saidrotating mold at a point eccentric to the axis thereof whilecontinuously withdrawing said casting from the lower end of said mold.9. The method claimed in claim 8 in which said mold is verticallyreciprocated while being rotated.
 10. The method claimed in claim 9 inwhich said mold, during reciprocation is moved downwardly more rapidlythan said casting is withdrawn therefrom.
 11. The method ofmanufacturing an article of manufacture which comprises the steps ofproducing a casting by the method claimed in claim 8, and hot drawingsaid casting.
 12. The method claimed in claim 11 in which glass is usedas a lubricant during said drawing.